title: Do changes in circulating biomarkers track with each other and with functional changes in older adults?
abstract: BACKGROUND
  It is unclear if changes in proposed circulating biomarkers of aging are strongly correlated to each other or functional change. We tested if biomarker changes track with each other and with functional measures over 9 years in older adults.
  
  
  METHODS
  Dehydroepiandrosterone sulfate (DHEAS), adiponectin, insulin-like growth factor 1 (IGF-1), IGF binding proteins 1 (IGFBP-1) and 3 (IGFBP-3), interleukin-6 (IL-6), cholesterol, and function (gait speed, grip strength, Modified Mini Mental Status Exam [3MSE] and Digit Symbol Substitution Test [DSST] scores) were measured in 1996-1997 and 2005-2006 in the Cardiovascular Health Study All Stars study (N = 901, mean [standard deviation, SD] age 85.3 [3.6] years in 2005-2006). Adjusted Pearson correlations illustrated if biomarkers tracked together. Multivariable linear regression demonstrated if biomarker changes tracked with functional changes.
  
  
  RESULTS
  Correlations among biomarker changes were mostly <0.2. In models with each biomarker entered separately, a 1-SD increase biomarker change was associated with change in function as follows: grip strength (DHEAS β = 0.61kg, p = .001; IL-6 β = -0.46kg, p = .012; cholesterol men β = 0.79kg, p = .016); gait speed (DHEAS β = 0.02 meters per second, p = .039; IL-6 β = -0.018 meters per second, p = .049); and DSST score (DHEAS women β = 1.46, p = .004; IL-6 β = -0.83, p = .027). When biomarkers were entered in the same model, significant associations remaining were as follows: grip strength (DHEAS β = 0.54kg, p = .005; IL-6 β = -0.43kg, p = .022); 3MSE score (IGF-1 β = 0.96, p = .04; IGFBP-3 β = -1.07, p = .024); and DSST score (DHEAS women β = 1.27, p = .012; IL-6 β = -0.80, p = .04).
  
  
  CONCLUSIONS
  Changes in biomarkers were poorly correlated, supporting a model of stochastic, independent change across systems. DHEAS and IL-6 tracked most closely with function, illustrating that changes in inflammation and sex steroids may play dominant roles in changes of these functional outcomes.
authors.affiliation: Bellefield Professional Building 4th Floor, 130 North Bellefield Avenue, Pittsburgh, PA 15213. jls196@pitt.edu.
authors.forename: Jason L
authors.initials: JL
authors.lastname: Sanders
authors.forename: Victoria
authors.initials: V
authors.lastname: Ding
authors.forename: Alice M
authors.initials: AM
authors.lastname: Arnold
authors.forename: Robert C
authors.initials: RC
authors.lastname: Kaplan
authors.forename: Anne R
authors.initials: AR
authors.lastname: Cappola
authors.forename: Jorge R
authors.initials: JR
authors.lastname: Kizer
authors.forename: Robert M
authors.initials: RM
authors.lastname: Boudreau
authors.forename: Mary
authors.initials: M
authors.lastname: Cushman
authors.forename: Anne B
authors.initials: AB
authors.lastname: Newman
mesh_terms: D052242:Adiponectin / Q000097:blood; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000097:blood*; D015415:Biomarkers / Q000097:blood*; D002784:Cholesterol / Q000097:blood; D003071:Cognition / Q000502:physiology*; D015331:Cohort Studies; D019314:Dehydroepiandrosterone Sulfate / Q000097:blood; D005260:Female; D005684:Gait / Q000502:physiology*; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D015850:Interleukin-6 / Q000097:blood; D008297:Male; D009483:Neuropsychological Tests; D011597:Psychomotor Performance / Q000502:physiology*; D013997:Time Factors
chemical_list: D052242:Adiponectin; D015415:Biomarkers; D018970:Insulin-Like Growth Factor Binding Protein 1; D018972:Insulin-Like Growth Factor Binding Protein 3; D015850:Interleukin-6; D019314:Dehydroepiandrosterone Sulfate; D007334:Insulin-Like Growth Factor I; D002784:Cholesterol
keywords: Biomarkers; Epidemiology; Functional performance; Inflammation; Longevity